Fig. 1: Structure of the TrkBtm dimer.
a The signal of the A440 amide group in the 1H-15N-HSQC spectrum of TrkBtm reveals two forms, S1 and S2, whose populations depend on the LPR. b Relative intensities of the S1 (orange) and S2 (blue) backbone amide signals in the NMR spectra as a function of LPR. At LPR = 90 the sample was diluted 2.5x. TrkBtm overall concentration decreased from 0.28 to 0.11 mM. c the hydrodynamic radii (RH) of an empty q = 0.3 DMPC/DHPC bicelle (obtained from translational diffusion of lipids, error bar shows the error of measurement, gray) and S1- (orange) and S2-containing (blue) bicelles (obtained from the rotational diffusion of proteins, error bars show the SD among the n = 6 considered residues). * indicates the statistical significance of the difference according to the Mann-Whitney test, p = 0.0202. The dashed lines denote the theoretical RH values obtained using the ideal bicelle model, as described30. d the natural logarithm of the penalty function χ2(k) calculated for n = 12 pairs of signals at several tested oligomer orders k = 2–5 of the S2 state28. In the gray area, the penalty function was not determined (*** indicates the statistical significance of the difference according to the two-sided t-test, p = 3.08 × 10-6). Error bars show the SD among the tested pairs of residues. e the spatial structure of the dimeric TrkBtm. One of the helices is shown as a blue cartoon and the other - either as an orange cartoon or as a surface painted according to its hydrophobicity (using the White-Wimley scale71). f Accessible surface area (ASA) of TrkBtm residues buried in the helix dimerization interface. The gray dashed line indicates the 50% threshold. The orange bars indicate the contact residues. Error bars indicate the SD among the set of n = 10 best NMR structures. g Closer view of the presumed key interactions supporting the TrkBtm dimer: V438 CαH-S441 Oγ polar contact and F445 stacking. Source data are provided as a Source Data file.
